Hi All,
Newbie and quite desperate husband of fraught lady BMW driver here hoping for advice.

I've seen many questions and responses on the forum on the subject of intermittent engine faults but none seem to relate to the problem my wife's car is suffering so hoping for some "pointers" from the many knowledgable people on this forum.

Symptoms are:
At between 60-70 mph, steady speed for a few miles, such as on motorway, engine will start to miss fire.
Within a second or two of the engine starting to miss the engine fault light comes on (steady) and the power is reduced.
Feels like failure on one cylinder rather than multiple.
Pulling over and stopping and restarting, the engine fault light has gone off and the engine is OK again.
Problem may or may not occur again on the same journey. Sometimes can occur many times.
On one trip when it occurred when i was driving I was able to 'force' the problem by, when travelling at around 60 mph, oscillating my foot on the accelerator a little.

The car has had all coils replaced on a recall has been into the main dealer many times but they've been unable to fix it. No fault codes are ever recorded. (According to the dealer and I've checked with an OBD / Torque App.).

1. Why are no engine faults ever recorded? Seems strange that the ECU has detected a failure and shut a cylinder down but then not recorded the fact. Any good reason for this?
2. Would an Indy garage have any more success finding the fault? Don't see why but maybe worth giving them a try.
3. Does anyone have any thoughts on what the cause may be? The problem occurs under similar circumstances so is very consistent, albeit intermittent.

My wife is extremely concerned (as i am) about being left stranded because of this fault, especially as she is now having to do a lot of motorway miles visiting her elderly mum. So unless I can get it resolved soon it looks like this otherwise very nice car will have to go.

Your help would be greatly appreciated.